Preterm birth is associated with bronchopulmonary dysplasia (BPD), a form of chronic lung disease that impacts the pulmonary and overall health of more than 10,000 infants in the US each year. The long-term objective of this Clinical Research Center (CRC) is translation of biochemical, genetic and bioinformatics research into innovative interventions that improve outcomes of extremely preterm infants at risk for long- term pulmonary morbidity. Our proposal focuses specifically on the urea cycle-nitric oxide (UC-NO) and glutathione (GSH) pathways as pivotal and interrelated mechanisms in the response of the developing lung to the extrauterine environment. Overall hypotheses: (1) Biochemical immaturity and functional genetic variation in the UC-NO and GSH pathways modulate the BPD phenotype spectrum; (2) The duration and degree of NO insufficiency and free radical excess predicts BPD severity and correlates with pulmonary morbidity after NICU discharge. To investigate our hypothesis, our CRC will enroll 250 infants with birthweights 510-1250 grams and follow the survivors through 1 year of life. Our hypothesis invokes an immature hepatic and gut synthetic capacity to make citrulline and GSH, functional genetic variations in the UC-NO and GSH pathways, nutritional deficiencies and the physiologic and environmental stress of preterm birth. The resultant NO deficiency and free radical excess alters pulmonary vascular and alveolar development. Our biomarker discovery concept includes (a) collection of plasma, urine, red blood cells, DNA and tracheal aspirates for measurements of NO and GSH precursor sufficiency, production of NO metabolites and GSH, functional genetic variants in these pathways, and biomarkers of in vivo oxidative stress and (b) validation of these biomarkers for diagnosis and long term prognosis of patients with BPD. A bioinformatics approach using machine learning and predictive modeling has been developed for respiratory phenotyping and risk stratification at 36 weeks and 40 weeks postmenstrual age and at 12 months after hospital discharge. Accomplishment of these goals will promote novel clinical trials design to test new therapies to prevent BPD and improve long term pulmonary health of infants born preterm. (End of Abstract) RELEVANCE: Each year in the US, more than 10,000 premature infants develop bronchopulmonary dysplasia (BPD), a chronic lung disease associated with prolonged and recurrent hospitalizations and lifelong alterations in lung function. This proposal will explore developmental, genetic and environmental interactions and identify biochemical markers to predict BPD development and severity, with the ultimate goal of designing new treatments to prevent BPD and improve long-term lung function in premature infants.